The primary purpose of the proposed continuation is the development and expansion of our knowledge of the interaction between the use of drugs of abuse, on the one hand, and associated drug-induced changes in sensory and motor function, on the other. This knowledge will come form conducting basic scientific investigations of the effects of drugs of abuse on sensory and motor function in nonhuman primates. The planned approach of these investigations involves the use of combined behavioral pharmacology and animal psychophysics research techniques, and their dedication to an experimental analysis of the effects of drugs of abuse on critical aspects of sensory and motor function. Procedurally, animal psychophysical procedures will be employed to obtain precise, quantitative assessments of the sensory/motor effects of common drugs of abuse, specifically ethanol, marijuana, and the opioids (including agonists, antagonists, and mixed agonists/antagonists). Past research has characterized the effects of acute doses of these compounds on sensory/motor function; the proposed research will extend this work by emphasizing the assessment of the effects of 1) chronic dosing regimens of ethanol and delta-9-THC on sensory and motor function, and 2) the interacting effects of drugs, including combinations of ethanol and delta-9-THC, and combinations of opioid agonists and antagonists. Basic aspects of sensory function examined will include 1) absolute auditory thresholds; 2) absolute visual thresholds; and 3) more complex auditory discriminations such as auditory frequency discriminations and speech sound discriminations, where appropriate. For all aspects of sensory function studied, reaction times of the motor response will be measured, thus providing and indicator of simple motor function for each type of psychophysical discrimination employed. This project will thus provide basic data on the effects of drugs on sensory and motor function across a range of drugs and doses, with particular emphasis on the chronic administration of drugs of abuse, and on drug interactions. The research will also yield information relevant to the clinical evaluation of drug-induced decrements in sensory and motor function, and will provide a basis for drug scheduling determinations.